Qt6 with Cmake submodule ReferenceError - qt

Question

I have a QT6 Qml with a Cmake File like this
cmake_minimum_required(VERSION 3.16)
project(appTEST VERSION 0.1 LANGUAGES CXX)
set(CMAKE_AUTOMOC ON)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
find_package(Qt6 6.2 COMPONENTS Gui Qml Quick REQUIRED)
set(CPPSOURCES
...)
set(CPPHEADERS
...)
qt_add_executable(appTEST
main.cpp
${CPPSOURCES}
${CPPHEADERS}
)
target_link_libraries(appTEST
PRIVATE
Qt6::Core
Qt6::Gui
Qt6::Quick
Qt6::Qml)
install(TARGETS appTEST
BUNDLE DESTINATION .
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
qt6_add_qml_module(appTEST
URI "Main"
VERSION 1.0
NO_PLUGIN
QML_FILES main.qml
)
add_subdirectory(content)
add_subdirectory(imports)
target_link_libraries(appTEST PRIVATE
contentplugin
impplugin
)
and the content module:
qt_add_library(content STATIC)
qt6_add_qml_module(content
URI "content"
VERSION 1.0
QML_FILES
...
)
and imp module :
set_source_files_properties(Constants.qml
PROPERTIES
QT_QML_SINGLETON_TYPE true
)
...
qt_add_library(imp STATIC)
qt6_add_qml_module(imp
URI "imp"
VERSION 1.0
QML_FILES
Constants.qml
...
)
with the constatnt.qml marked as a Singleton like this:
pragma Singleton
import QtQuick 6.3
QtObject {
...
}
so I expect to be able to import imp on any page and have access to constatnt.qml properties.
but in run time get this error
ReferenceError: Constants is not defined
note tath I tried to adopt the structure from Qt Design Studio default project template.